This invention relates to a device for withdrawing a fiber web from a web delivering assembly of a carding machine and for gathering the web into a sliver with the aid of a guide element which is arranged immediately downstream of the web delivering assembly and which has a guiding face which traverses the plane of the web.
In a known web guiding device, as disclosed in U.S. Pat. No. 3,946,464, the guide element is formed of at least two transport belts. Those reaches of the one and the other transport belt which are arranged tangentially to the web delivering assembly, run in opposite directions. In this device the guide element has at least one moving guiding face. This arrangement requires that the transport belts run on driven rollers; such a structure is prone to malfunctioning. Further, the transport belts have to be maintained under constant tension which requires additional work and maintenance. Also, the entire apparatus is of complex and expensive structure. It is a further disadvantage that the guiding faces of the transport belts are planar so that air may impinge from above downwardly without hindrance on the web emerging from the web delivering assembly. This disadvantage is particularly pronounced in case the web leaves the delivering assembly at high speeds.
In another known web guiding device, disclosed in U.S. Pat. No. 3,196,492, the card web is discharged by the doffer of a carding machine and is supported by guiding faces. This guiding device adjoins the doffer and extends to the calender roll pair. For this purpose, between these components there is arranged an asymmetrically structured planar triangular sheet metal web guide member which has two lateral web guiding means constituted by upwardly bent edges. The longitudinal edge rims which have a somewhat downwardly oriented inclination, thus form an acute angle with the axis of the doffer so that the entire device forms a funnel-like structure. The web guiding device is open between the two edges, so that the web which slides over the sheet metal guide is exposed to air from above. As a result, the web may, particularly in case of high speeds, break out upwardly. It is known that the fiber web which is discharged by the carding machine at high speeds has to be gathered with an equally high speed. As the web slides over the sheet metal guide, it may suffer accumulation or breakage caused by local differences in adhesion. These phenomena adversely affect the flow of production as well as the quality of the fiber web obtained. A withdrawal and a gathering of a web running at high speeds is therefore not feasible with this known device.
In a further web guiding device disclosed in U.S. Pat. No. 3,840,942 a pair of guide elements detached from one another are arranged at either side of the web discharged by the crush rolls of a carding machine. There are provided adjusting devices which move the guide elements from an outer position in which no web condensing effect exists into an inner position in which the web is gathered to an approximately T-shaped sliver. Both guide elements are significantly shorter than the length of the crush rolls and for this reason they have to be arranged at a certain distance from the crush rolls in order to be capable of gathering the entire web emerging from the crush rolls. Since the web is exposed to a strong air current in this device, the latter is not adapted for high web speeds, since the web would break under the effect of the air.